Digital Video Tampering Detection Techniques

Introduction

We can define video many ways, Time varying image is known as video or Changing of Image in temporal domain is known as video or Transformation of 4 D(X,Y,Z,T) physical object in 3 D(X,Y,T) is known as video.(T-temporal domain, (X,Y,Z)- Spatial Domain).An image is defined by spatial coordinates(X,Y)and its intensity function F(X,Y). When (X,Y) and intensity value is discrete at every point in image plain then we call image digital image(Gonzalez & Woods,2002). Due to high availability of low cost s/w editing tools, it is very easy to tamper the digital video. Some modification in video does not lead to malicious tampering in video for example modification in video to increase quality of video. Illegal, improper and malicious intension for modifying video to conceal some important information, event or object is known as video tampering. According to video we can divide video tampering detection techniques in two categories: first one is active video tampering detection techniques and second one is passive video tampering detection techniques. In active video tampering detection techniques we use the concept of digital Signature and digital watermark or combination of both. But in passive video tampering detection techniques we do not have any information regarding digital signature and digital watermark. If we have no information of camera from which video was taken then we call it blind video. The techniques used to detect tampering in blind and passive video is known as blind and passive video tampering detection techniques. Video tampering and tampering detection both are tough in comparison to image tampering and tampering detection. People follow the concept seeing is believing but video tampering has disproven this concept. Video tampering detection is necessary because people are using video tampering to defame popular person, concealing important information and presenting it as proof in the court to get judgment in his favors. If we have active video then it is easy to detect tampering by using digital signature and digital watermark, but if we have no information about source camera and video does not contain digital signature or digital watermark then it is very challenging to detect video tampering. Generally Internet streaming video does not contain information regarding source camera, digital signature and digital watermark. Blind and passive video tampering detection is new era for researcher and research work in this area is going on. In video mainly three types tampering arise first one is spatial tampering second one is temporal tampering and last is spatial-temporal tampering. In spatial tampering we generally focus on intra frame but in temporal and spatiotemporal we focus on interframe. In passive video spatial tampering detection techniques can be roughly categorized into five category 1) Pixel Based 2) Format based3) H/W or Camera based 4) Physics based 5) Geometric based H.Farid(2009).In pixel based tampering detection we mainly focus on intra frame and spatial coordinate of intra frame. The various video tampering approach in this category is Copy Move, Splicing, and Resampling. Format based technique include Double MPEG compression, MPEG Blocking etc. H/W or Camera based tampering detection use Sensor Noise, Color filter array, Camera response function, Chromatic aberration, White balancing and gamma correction features of Camera used in shooting video. In physics based video tampering detection we mainly focus on light direction and light environment for video tampering detection. In geometric based tampering detection we mainly focus on principal point and Metric measurement. If we want to detect temporal tampering in passive video then we can use the concept of motion compensated edge artefacts (MCEA) for I, P and B frames in video.